3 ms·

Sorry if I missed it, but what is the defined purpose of the s3_5_c15_c10_1 register? Or is it just general purpose?

by afandian 5y ago

Cthulhu_ 5y ago
I googled it for you and err, came up blank, there's just two code references in some ASM code, the rest points to this resource. Weird, I would have thought things like this would have public documentation.
- pthariensflame 5y ago
  https://news.ycombinator.com/item?id=27287519 https://news.ycombinator.com/item?id=27287519
pthariensflame 5y ago
It’s not a standard ARM register; it’s implementation-defined and nobody gave it a meaningful name. It appears to do nothing much.
- exikyut 5y ago
  Then why not unofficially standardize its use in GCC and Clang's register-pooling subsystem?
  - saagarjha 5y ago
    Because GCC and Clang don't get to decide what hardware does with the register…
marcan_42 5y ago
It's an implementation-defined register, which means it's up to Apple to define it. We have no idea what it does; we haven't observed any visible effects from flipping those bits. Given that it's per-cluster, we can infer that it has something to do with cluster-specific logic. Perhaps memory interface or power control. There are hundreds of Apple implementation-defined registers; we're documenting them as we learn more about them [0] [1] [2] [0] https://github.com/AsahiLinux/m1n1/blob/main/tools/apple_regs.json https://github.com/AsahiLinux/m1n1/blob/main/tools/apple_reg... [1] https://github.com/AsahiLinux/docs/wiki/HW%3AARM-System-Registers https://github.com/AsahiLinux/docs/wiki/HW%3AARM-System-Regi... [2] https://github.com/AsahiLinux/docs/wiki/HW%3AARM-System-Registers-Dumps https://github.com/AsahiLinux/docs/wiki/HW%3AARM-System-Regi...